Direct impact load tests on mechanical hybrid rockbolts

Authors: Knox, G; Hadjigeorgiou, J

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DOI https://doi.org/10.36487/ACG_repo/2465_26

Cite As:
Knox, G & Hadjigeorgiou, J 2024, 'Direct impact load tests on mechanical hybrid rockbolts', in P Andrieux & D Cumming-Potvin (eds), Deep Mining 2024: Proceedings of the 10th International Conference on Deep and High Stress Mining, pp. 467-478, https://doi.org/10.36487/ACG_repo/2465_26

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Abstract:
A mechanical hybrid rockbolt is comprised of a tendon mechanically anchored within a friction unit. The rockbolt is driven into the pre-drilled borehole using a percussive force and can be efficiently and effectively installed in conditions where the application of resin cartridges is either challenging or impractical. The potential for higher installation rates and quality in friable or fractured rock masses, compared to resin grouted rockbolts, has resulted in the use of mechanical hybrid rockbolts for both static and dynamic conditions. Mechanical hybrid rockbolts are installed using percussion techniques. On completion of the percussive drive cycle, a rotation is applied to the tendon to activate the mechanical anchor. The frictional resistance of the friction unit generates the reactive force against which the mechanical anchor is activated with the tendon mechanically coupled at the distal and proximal end. Currently, there are limited data on the performance of mechanical hybrid rockbolts under different loading conditions in a controlled environment. This paper presents the results of a series of tests on mechanical hybrid rockbolts under direct impact loading. Direct impact continuous tube tests are one of the tools used to understand the performance of rockbolts under seismic loads. They are typically used to simulate a strainburst event where the seismic load acts on the interface (face plate) between the surface support and the rock reinforcement element. These results complement earlier work by the authors that focused on quasi-static axial and shear tests.

Keywords: mechanical hybrid rockbolt, impact testing

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